Ex.No. 1    GENERAL CHARACTERS OF FUNGI

Fungus is a Latin word which means mushroom. Fungi are achlorophyllous, nucleated, branched, unicellular or multicellular microorganisms that may reproduce by sexually or asexual and eukaryotic organisms. Fungus cell wall is made up of chitin and Oomycetes fungus cell wall is made up of cellulose.

Morphology of fungi

1.       Thallus – Vegetative/ somatic body of the fungus.

a.       Unicellular  -  singe celled (E.g.. Yeast)

b.       Filamentous– thread form of fungi ( E.g. Eumycota)

c.       Holocarpic thallus – Entire thallus is converted into reproductive structure (Yeast)

d.       Eucarpic thallus – The thallus is differentiated into vegetative part which absorbs nutrients and a reproductive part which forms reproductive structure. (Pythium)

2.        Hyphae – It is a tubular filament thin tube with the layer of protoplasm and cytoplasm.

3.       Mycelium – Mass of hyphae are collectively called as Mycelium.

a.       Septate mycelium – Presence of cross walls (Higher fungi)

b.       Aseptate mycelium or Coenocytic mycelium – Without cross walls (Oomycetes, Zygomycetes)

c.       Monokaryotic – Contains single nucleus

d.       Dikaryotic – Contains pair of nuclei

e.       Intercellular mycelium – In between the cells

f.        Intracellular mycelium – Inside the host

4.       Septal pore – Septa have pores that allow cytoplasm, organelles and some time nuclei pass through the body of the fungus

a.       Simple pore septum – A septum having circular pore in the middle. (Ascomycetes)

b.       Dolipore or complex pore septum – A septum having a central pore is swollen and forming a barrel shaped structure with open ends which is surrounded by a thin membrane is called parenthesome. (Basidiomycetes)

5.       Flagella – The motile cells in the lower fungi responsible for locomotion.

a.       Whiplash type – flagellum with a smooth continuous surface

b.       Tinsel type – flagellum with a surface covered hair like structure

Aggregation and Modification of fungal hyphae

                In most fungi, during certain stages of its life cycle the mycelium become organised into loosely or compactly woven tissues which are distinguishable from the normal hyphae composing a thallus.

1.       Plectenchyma – It’s a false tissue are formed by aggregation of hyphae. It is two types.

a.       Prosenchyma – Parallel to one another forming a loose tissue (E.g.. Stromata)

b.       Pseudoparaenchyma – Hyphal elements are oval or isometric shape and closely packed. Eg. Pycnidium)

2.       Rhizomorph – Root like structure of compact masses. (E.g.. Armillariella mellea, Ganoderma)

3.       Sclerotia – It is a compact, hard resting structure made up of pseudo parenchymal tissues.

Disease name	Causal organism	Sclerotia structure and colour
Rice sheath blight	Rhizoctonia solani	Brown colour and irregular structure
Pulses root rot	Rhizoctonia bataticola	Black colour
Ground nut collar rot	Sclerotium rolfsii	Brown colour and mustard shaped
Ergot or sugary disease of cumbu	Claviceps fusiformis	Black colour, the grains are replaced by sclerotia and look like a grain structure (false grain).

4.       Chlamydospore – Fusarium produces resting structure is known as Chlamydospore. They are produced either singly or in chains and may be terminal or intercalary in the hyphae.

5.       Appressorium – It is a special structure for attachment on host surface at the tip of germ tube.

6.       Haustoria – It is a knob like structure of the hyphae present in the host cells and absorbs nutrients from the host.